The present invention relates to fuel injectors for injecting fuel into the fuel intake systems of internal combustion engines; more particularly, to a fuel injector having a plurality of components disposed on the outer surface of a thin tubular body; and most particularly to a fuel injector wherein the components external to the tubular body are encapsulated and held in proper functional relationships by a surrounding shroud formed of a structural adhesive polymer.
Fuel injectors are well known components of internal combustion engines, being useful for repeated injection of metered amounts of liquid fuel into the fuel intake system. Typically, one fuel injector is provided for each cylinder of an engine, being mounted with entry into either the engine intake manifold or directly into the firing chamber. Each fuel injector includes a solenoid-operated poppet valve which receives an electrical signal coordinated with signals to all other injectors to dispense fuel in synchrony with the firing of the engine. The valve is opened by energizing of the electric solenoid and is closed by a mechanical coil spring.
In the known art, a fuel injector generally includes a central tubular body having connection to a fuel supply at one end and a valve seat at the other end. A valve head matable with the seat is attached to a solenoid slug, or core, which is slidably disposed within the tube to open and close the valve. The core is hollow and is ported above the valve head to permit fuel to be supplied axially through the core to the valve. A portion of the tube is surrounded by the electrical windings of a solenoid coil, and the core extends axially by a distance into the coil. Energizing the windings causes the core to move farther into the coil, thus opening the valve and injecting fuel into the engine. Typically, the windings are positioned and retained axially on the outer surface of the tube by an enclosing housing which is spot welded to the tubular body.
Several practical problems arise in optimizing the configuration and construction of such a fuel injector. Because the windings are outside the tubular body and a solenoid pole piece and core are inside, the body must be formed of a non-ferromagnetic material, such as a 300-series stainless steel. To maximize the strength of the axial magnetic field within the solenoid, the body wall is formed as thin as is structurally feasible, typically being 300-400 m thick. However, because the tubing is thin, the wall may be breached inadvertently during welding of components to it, resulting in a leaky and thus defective injector. Further, the tubular body must be sufficiently rugged to withstand the various forces of torque and shock which the injector must undergo during its assembly and working lifetime.
What is needed is a simple and cost-effective means for providing auxiliary structural support to the tubular body of a fuel injector, thus allowing further thinning of the body wall to increase the effective strength of the solenoid magnetic field; reducing the number of components to be manufactured, inventoried, and assembled; and also obviating the need for welding a windings housing to the body.
The present invention is directed to a fuel injector for an internal combustion engine wherein components external to the tubular body are positioned, joined, and retained on the body, and wherein the tubular body is structurally reinforced, by being encapsulated together in a molded shroud formed of a structural adhesive polymer.